The invention relates generally to wheel engaging apparatus for use with vehicle towing systems. More specifically, the invention concerns wheel cradles for towing systems wherein the towed vehicle is lifted and towed principally by its wheels.
The concept of using detachable, inwardly facing L-shaped wheel cradles in a wheel lift towing system was first introduced in U.S. Pat. No. 4,679,978--Holmes et al., assigned to the same assignee as this invention. So-called "wheel lift" towing approaches avoid the need for the conventional tow truck sling assembly by using wheel engaging structures or "wheel cradles" which engage the fromt or rear wheels of a vehicle to be towed to lift the wheels and therefore one end of the vehicle substantially without engaging any other portion of the vehicle. The '978--Holmes et al. patent disclosed such a wheel lift tow assembly mounted to the frame at the rear of a tow vehicle and moveable vertically. The tow assembly of the Holmes et al. disclosure included a telescopic tow bar extended and retracted from the rear of the vehicle and a cross arm pivotally mounted intermediate its ends about an upwardly extending axis to a rear portion of the telescopic tow bar. L-shaped wheel cradles were releasably connected to end portions of the cross arm in the Holmes et al. patent.
U.S. Pat. No. 4,637,623--Bubik discloses a later version of a wheel lift towing assembly using substantially L-shaped removable wheel cradles having the capability for pivoting in a horizontal plane from a laterally reomte position spaced outwardly from the sides of the vehicle to be towed.
However, the Bubik arrangement requires insertion of the wheel cradle into coupling devices associated with the cross arm in a direction substantially perpendicular to a longitudinal axis of the cross arm -- i.e., in a direction substantially parallel to the longitudinal axis of the towed vehicle. This required insertion approach makes cradle attachment to the cross arm of the towing vehicle difficult when obstructions prevent adequate clearance immediately adjacent the outside lateral surfaces of the wheels to be engaged.
While known systems employ insertion of the wheel cradle parallel to a longitudinal axis of the cross arm, such systems utilize an extra cradle side arm extension extending parallel to the cross arm axis for insertion into a cross arm slot. Furthermore, in such known systems, the wheel cradle is not adjustable to a plurality of angular positions relative to the crossbar.
Additionally, there is seen to be a need for a convenient back-up safety line arrangement for providing additional coupling security between towing and towed vehicles.